A copper phthalocyanine is a material widely used in the fields such as a pigment, a semiconductor, a photoreceptor, a recording medium, a solar cell, a liquid crystal, and a catalyst. Because the copper phthalocyanine has a clear hue, a high coloring power, and a fastness, it is used every field as a blue pigment.
In recent years, in order to further express or improve characteristics of the copper phthalocyanine, attempts have been made to produce a composite phthalocyanine added thereto with a phthalocyanine having a different metal.
In Patent Document 1, a blue pigment or paint composition comprising a cobalt phthalocyanine and a copper phthalocyanine is disclosed; and in Patent Document 2, a pigment composition for a color filter comprising an alpha-type cobalt phthalocyanine pigment and an epsilon-type copper phthalocyanine pigment is disclosed.
The copper phthalocyanine particles disclosed in Patent Document 1 and Patent Document 2 are produced by a crushing method. In order to improve the characteristics thereof, the particles are definitely required to be microparticles; however, with the crushing method, microparticles having the size of 100 nm or less, especially 50 nm or less, are difficult to be produced. Moreover, even if the microparticles as mentioned above could be produced, not only an enormous energy is required in the production thereof, but also a strong force is applied to the microparticles, resulting in poor crystallinity so that intended characteristics cannot be obtained. Therefore, in a recent trend of requiring a higher performance, there may be a limit in the crushing method.
On the other hand, as the one method to produce the copper phthalocyanine microparticle not having the drawbacks of the crushing method as mentioned above, a crystallization method by a poor solvent is known. In this method, the copper phthalocyanine microparticle is separated by mixing a raw material solution in which the copper phthalocyanine is dissolved in a good solvent being capable of dissolving the said compound with a poor solvent having a lower solubility to the same than the good solvent (Patent Document 3).
However, even in the crystallization method by a poor solvent, there still remains a problem that crystal growth of the copper phthalocyanine microparticle further takes place in an organic solvent. That is to say, because the copper phthalocyanine undergoes the crystal growth in an organic solvent, the microparticle becomes coarse so that the color characteristics are deteriorated.
In order to suppress the crystal growth, use of a crystal growth suppressor to the copper phthalocyanine may be contemplated. In Patent Document 4, a phthalocyanine having a different metal is suggested as the crystal growth suppressor. However, the method disclosed in Patent Document 4 is different from the crystallization method by a poor solvent as mentioned before. Therefore, in the case that the copper phthalocyanine is produced by the crystallization method by a poor solvent, there is no description with regard to in which process and with what procedure the phthalocyanine having a different metal is applied to the copper phthalocyanine so as to suppress the crystal growth.
For example, there is no description with regard to the ratio of the phthalocyanine having a different metal to the copper phthalocyanine. When the ratio of the phthalocyanine having a different metal to the copper phthalocyanine is high, the crystal growth can be suppressed, but the color characteristics are deteriorated due to the effect of the phthalocyanine having a different metal. On the other hand, when the ratio of the phthalocyanine having a different metal to the copper phthalocyanine is low, the crystal growth of the copper phthalocyanine microparticle cannot be suppressed, so that improvement of the color characteristics thereof cannot be expected. Patent Document 4 discloses no proposal with regard to the way how to solve these problems.
Meanwhile, as disclosed in Patent Document 5 and Patent Document 6, a micro reactor with a type of a forced thin film is known; in this reactor, a fluid is made to react in a thin film fluid formed between processing surfaces which are disposed in a position they are faced with each other so as to be able to approach to and separate from each other, at least one of which rotates relative to the other. The phthalocyanine microparticle produced by the micro reactor like this is finer and more homogeneous as compared with those produced by other conventional methods, so that, with this method, there are merits of further higher coloring strength and color development.
However, with this method on the contrary, the Ostwald ripening is facilitated thereby tending to cause increase in the size of the microparticle in the organic solvent and to cause necking. Accordingly, there is a dilemma that it is difficult for the copper phthalocyanine produced by the micro reactor thereby having finer and higher homogeneity to express the expected color characteristics.
In fact, the transmission/absorption spectra of the copper phthalocyanine microparticle of Patent Document 5 or Patent Document 6 in a visible light region has, in view of the absorption spectrum thereof, the highest peak near the wavelength of 600 nm and the second highest peak in the region of about 660 to 700 nm. In view of the transmission spectrum, the highest transmittance is in the region of 400 to 500 nm with the difference between the highest and lowest transmittance being 80% or more, whereas the transmittance increases again in the region of 620 to 800 nm. Therefore, the copper phthalocyanine has a reddish color in spite that it is expected to be a coloring material intrinsically having a blue to cyan color; and thus, improvement of the color characteristics in order to give a clearer blue color with eliminating the reddish color has been wanted.
In addition, especially in the case that the copper phthalocyanine was produced by using the micro reactor, the separation reaction took place rapidly; and thus, mere addition of the phthalocyanine having a different metal in the way as described in Patent Document 4 could not suppress the crystal growth of the separated microparticle, so that improvement of the color characteristics of the copper phthalocyanine could not be accomplished.